252 AN AMERICAN TEXT-BOOK ON PHYSIOLOGY. 



From this brief description it will be seen that osmosis supposes the existence 

 of two miscible liquids lying on opposite sides of a membrane. In the 

 alimentary canal we have this arrangement. The mucous membrane rep- 

 resents the dialyzing membrane ; on one side is the blood or the lymph, and 

 on the other side are the contents of the stomach or the intestine. If in 

 the latter there is more sugar, let us say, than in the blood, then, according 

 to the principles of osmosis, the sugar will tend to dialyze through the mucous 

 membrane into the blood, and a quantity of water corresponding to its endos- 

 motic equivalent will pass back into the canal. The fact that the blood is 

 in rapid movement should promote the rapidity of dialysis, for the obvious 

 reason that it tends to prevent an equalization in composition; just as in 

 ordinary osmosis, if the parchment tube containing the substance to be 

 dialyzed is swung in running water, the osmosis will be more complete 

 and more rapid than when it is suspended in a given bulk of water which 

 is not changed. 



With this brief exposition of the meaning of the terms diffusion, osmosis, and 

 dialysis, let us pass on first to a consideration of the facts known with reference 

 to the actual absorption that occurs in diiferent parts of the alimentary canal. 



Absorption in the Stomach. In the stomach it is possible that there 

 might be absorption of the following substances: water; salts; sugars and 

 dextrins, which may have been formed in salivary digestion from starch, or 

 which may have been eaten as such ; the proteoses and peptones formed in 

 the peptic digestion of proteids or albuminoids. In addition, absorption of 

 soluble or liquid substances drugs, alcohol, etc. which have been swallowed 

 may occur. It was formerly assumed without definite proof that the absorp- 

 tion in the stomach of such things as water, salts, sugars, and peptones was 

 very important. Of late years a number of actual experiments have been 

 made, under conditions as nearly normal as possible, to determine the extent 

 of absorption in this organ. These experiments have given unexpected results, 

 showing, upon the whole, that absorption does not take place readily in the 

 stomach- certainly nothing like so easily as in the intestine. The methods 

 made use of in these experiments have varied, but the most interesting results 

 have been obtained by establishing a fistula of the duodenum just beyond the 

 pylorus. 1 Through a fistula in this position substances can be introduced into 

 the stomach, and if the cardiac orifice is at the same time shut off by a ligature 

 or a small balloon, they can be kept in the stomach a given time, then be 

 removed, and the changes, if any, be noted. After establishing the fistula in 

 the duodenum food may be given to the animal, and the contents of the 

 stomach as they pass out through the fistula may be caught and examined. 

 The older methods of introducing the substance to be observed into the 

 stomach through the oesophagus or through a gastric fistula were of little use, 

 since, if the substance disappeared, there was no way of deciding whether it 

 was absorbed or was simply passed on into the intestine. 



1 Compare V. Mering: Ueber die Function des Magens, 1893; Edkins : Journal of Physiology, 

 1892, vol. 13, p. 445 ; Brandl : Zeitschri/t fur Biologic, 1892, vol. 29, p. 277. 



